1. Field of the Present Invention
The present invention generally relates to Asynchronous serial devices, and more specifically to a method of verifying the baud rate for communication of data by a serial device residing within a data processing system.
2. History of Related Art
Data processing systems, in general, use serial interface devices for communicating data to external devices such as keyboards. The rate at which the data is communicated to an external device is referred to as a Baud rate. Baud rate, as referred to hereinafter, refers to the unit of modulation rate corresponding to one unit interval per second.
Typically, the serial interface device of a data processing system has some variation of an internal clock and other circuitry for enforcing or maintaining a selected baud rate. Unfortunately, this internal clock or other circuitry may become unstable or defective for any number of reasons. When this occurs, the baud rate at which the serial interface device communicates information to an external device can become inaccurate or unstable. This results in an inability to communicate with the external device. Unfortunately, end users of the data processing system often lack access to expensive complex testing equipment for determining problems occurring within the serial interface device. Accordingly, the current methods employed for determining whether a serial interface device is defective must be simple and cost effective. One such method is the "wrap plug" test. A "wrap plug" test involves connecting the transmit and receive pins of the serial interface device to one another. This type of test, however, will only verify that accurate data is being transmitted by the serial interface device. Thus, the "wrap plug" test fails to detect a serial interface device which has an inaccurate clock or other circuitry for maintaining baud rate, since the data transmitted and the data received will be accurate. This often results in the end user spending endless hours and perhaps money to debug their data processing system for a problem which had not been revealed by the "wrap plug" test.
It would, therefore, be a distinct advantage to have a cost effective method and system for testing the accuracy of the baud rate for a serial interface device of a data processing system. The present invention provides such a method and system.